1. Field of the Invention
The present invention relates to a product with a concave-convex pattern on its surface, a method of forming the concave-convex pattern, and a method of manufacturing a decoration sheet used for forming the concave-convex pattern.
2. Description of the Related Art
An interior part such as a dashboard of an automobile is formed by synthetic resin in terms of light weight and mass production. In order to obtain expensive appearance, stateliness and warmness, a fine concave-convex pattern such as a satin finished surface and grain is formed on a surface thereof. The resin product can be molded by forming a concave-convex pattern of the product on the surface of a die by etching and the like, and a pattern in which the concave part and the convex part are reversed.
However, the die is difficult to be manufactured in terms of cost and time at a trial stage of the automobile. Thus, the concave-convex pattern is formed on the surface of a trial product by attaching a sheet formed with a concave-convex pattern at the trial stage of the automobile. If the sheet is thick, the relevant surface tends to differ from the surface of a mass produced product in terms of quality and image. Furthermore, the cost increases if the concave-convex pattern is complex when the sheet is manufactured from the die.
The applicant has previously proposed a thin decoration film formed with a concave-convex pattern on a surface thereof, as shown in FIG. 6 (see Japanese Examined Patent Publication No. 2001-150891). In the disclosure, the concave-convex pattern is formed on a photosensitive resin film in a printing method including exposure, washing and drying, and coating is performed from above. A final product to be mass produced can be imaged by looking at a trial product with the decoration film attached on the surface thereof, and thereby a design can be determined.
However, the conventional method has the following problems.
The concave-convex pattern surface tends to be rough on the decoration film shown in FIG. 6, since a concave part (24) between adjacent convex parts (22) (22) is drastically depressed from the upper end of the convex part (22). A feeling that the image of the pattern is slightly different from a desired fine pattern of the satin finished surface, grain and the like may arise since the height of the convex part (22) and the depth of the concave part (24) are also even.
Furthermore, when mass producing the dashboard of the automobile by means of a die, the concave-convex pattern on the surface of the dashboard cannot be formed with the convex parts of even height and the concave parts of even depth on the entire surface of the die due to necessity of taking the three dimensional product out from the die. Specifically, assume a dashboard, or a final product (1) having a bent part as shown in FIG. 7. The die for molding the dashboard is released upward and downward.
In this case, if the height of the convex part (22) positioned at the flat portion A and the convex part (22) positioned at the lower end of the inclined portion B are the same, die release becomes difficult as the convex part (22) positioned at the inclined portion B becomes an obstruction. Therefore, the convex part (22) positioned at the lower end of the inclined portion B is formed lower than the convex part (22) positioned at the flat portion A. Thus, a stringent quality is demanded also for the trial product so that the heights of the convex parts (22) are changed depending on the location so as to be the same as the concave-convex pattern on the surface of the mass produced product.